A jig for calcining an electronic component is required to be unreactive with ceramic electronic components to be calcined in addition to having heat resistance and mechanical strength. When an electronic component work such as a dielectric is contacted and reacted with the calcination jig, a problem arises that the characteristics may be deteriorated due to the fusion or the composition fluctuation of the work.
The substrate for the jig for calcining the electronic component generally includes an alumina-based material, an alumina-mullite-based material, an alumina-magnesia-based-material, an alumina-mullite-cordierite-based material and a combination thereof.
In order to prevent the reaction of the jig with the work, a method of coating zirconia (zirconium oxide, ZrO2) on the surface layer is employed. Although the reactivity of the zirconia with the substrate is low, the coating of the jig may be cleaved or peeled off under an environment in which the repeated heat cycles take place due to the larger difference between thermal expansion coefficients of the substrate and the zirconia. When the jig is repeatedly used and the particles contained in the surface zirconia layer has a lower particle removal resistance or a lower abrasion resistance, the fine particles are mixed into electronic components to cause a severe problem. The phase change from a monoclinic system to a tetragonal system takes place in the zirconia at around 1100° C. As a result, a problem arises that the change of the thermal expansion coefficient accompanied with the phase transformation due to the repeated heat cycles eliminates the coated layer of the zirconia to generate cracks so that electronic components to be calcined are likely to be influenced by the substrate. The use of non-stabilized zirconia easily takes place the degradation to lower the anti-grain detaching property.
An application method, a dip-coating method and a spray-coating method are used for forming the zirconia surface layer (or zirconia film) on the substrate surface of the jig for calcining the electronic component. In these methods relatively inexpensive and suitable for industrial production, the anti-grain detaching property and the anti-abrasion property of the formed zirconia surface layer may be insufficient. Especially, under the circumstance in which the heat cycles are repeatedly loaded on the jig for calcining the electronic component, the zirconia surface layer may be peeled off from the substrate and the grains may be detached.
When the zirconia surface layer is formed by using relatively coarse particles, the zirconia surface layer does not become compact, and a plenty of bubbles are formed to absorb the difference of thermal expansion from the substrate. However, the adhesiveness between the zirconia film and the substrate is inferior together with the decrease of the sintering property, thereby generating a cause of peel-off.
Patent Document 1: JP-A-10(1998)-13957 (paragraphs 0005 to 0007)
Patent Document 2: JP-A-2003-226586 (claim 1)
Patent Document 3: JP-A-2001-213666 (claim 1)
Patent Document 4: JP-A-2003-73183 (claim 2)